When a person is shot, stabbed or injured by shrapnel in the chest, the wound often times penetrates a sufficient distance into the chest cavity to puncture the parietal pleura, visceral pleura, and the lungs. In some cases two wound holes are formed, an entry and an exit hole. A wound hole(s) that penetrates the chest cavity and parietal pleura allows air and/or blood to flow freely into the chest cavity, the pleural space, and possibly the lungs.
The condition wherein air penetrates into the pleural space between the lung and the chest wall through a wound hole in the chest wall is referred to as an open pneumothorax. When an open pneumothorax occurs, the normal mechanism by which the lung expands is lost; i.e., the fluid adhesion of the pleural surface of the lung to the pleural surface of the chest wall. Thus, the affected lung does not expand when the patient inhales and respiratory distress becomes severe and possibly fatal.
For patients with an open wound to the chest, the severity of the open pneumothorax that develops can be minimized by sealing the open wound via an occlusive bandage prior to transport. The occlusive bandage is used to eliminate air penetrating into the pleural space through the wound hole when the patient inhales.
However, if the intake of air into the pleural space is not entirely eliminated, additional air may be trapped in the pleural space, thus causing the pressure in the affected chest cavity to rise, a condition referred to as tension pneumothorax. If the pressure in the chest cavity exceeds normal pressure, blood flow from the heart to the lungs may be halted, with death rapidly following. Thus, it is imperative that when treating an open pneumothorax, that the wound is appropriately sealed in a manner which eliminates air from penetrating into the pleural space through the wound hole.
The current day medical procedures used by first responders to treat an open pneumothorax are occlusive type dressings. For example, (1) petrolatum gauze dressing, (2) a sterilized aluminum foil dressing, or (3) a folded universal dressing placed over the wound. The gauze dressing, foil or universal dressing is taped to the skin on all four sides of the wound. By taping the dressing on all four sides, the first responder is attempting to eliminate air penetrating into the pleural space through the wound.
Yet, in most instances, this type of dressing is ineffective. It either (1) does not totally eliminate air entering the pleural space through the wound; (2) eliminates air penetrating into the pleural space through the wound yet does not allow the already trapped air to escape; or (3) a combination of both. These defects could cause a more serious tension pneumothorax to develop which leads to respiratory insufficiency and heart failure. Consequently, a need exists for a method and apparatus for successfully treating an open pneumothorax that can be used by first responders, which totally eliminates the intake of outside air into the pleural space via the wound hole yet allows already trapped air to escape.
In addition to developing a tension pneumothorax by using defective dressings as discussed above, a patient with an open chest wound and a severe lung laceration may also develop a tension pneumothorax in a different manner. For instance, the bandage may have eliminated air from entering the pleural space through the wound hole, yet if lacerated, the lung will continue to leak air into the pleural space. Consequently, every time the patient inhales, more air becomes trapped in the pleural space, causing more pressure to be exerted on the lacerated lung. This increased pressure on the lacerated lung forces the lung to collapse until reduced to a ball 2-3 inches in diameter. At this point of collapse, pressure in the affected chest cavity begins to rise, the collapsed lung is pressed against the heart and the lung on the opposite side, compressing the remaining uninjured lung. If the pressure in the chest cavity exceeds the normal pressure of the blood returning to the heart, blood flow from the heart to the lungs may be halted, with death rapidly following.
To successfully prevent a tension pneumothorax from developing, the air flow into the pleural space via the wound hole must be eliminated, but the air coming from the lacerated lung must be allowed to escape the pleural space via the wound hole. The method of treatment currently used by first responders is the same type of dressing used to treat an open pneumothorax except it is taped on only three sides of the wound. The untaped side of the bandage theoretically allows air to exit the pleural space through the wound hole when the patient exhales. As the patient inhales, the three sided dressing theoretically collapses against the wound, thus prohibiting air from entering the pleural space through the wound hole.
In most instances, three sided dressings are ineffective. Initially, the amount of blood that normally accompanies the chest wound prohibits the tape from securely attaching the dressing to the patient. Secondly, when the petrolatum gauze dressing is opened, it becomes creased, making it less form fitting to the body. Consequently, air can both enter and exit the chest cavity because the petrolatum gauze is not sucked against the wound when the patient inhales. Petrolatum is also necrotizing to the lung tissue. If petrolatum penetrates the wound and contacts the lung tissue, the lung tissue may die.
In addition to a tension pneumothorax, a patient with a chest wound may also experience a hemothorax. A hemothorax is the presence of blood in the pleural space. The blood in the pleural space may come from lacerated vessels in the chest wall, from lacerated major vessels within the chest cavity itself, or from a lacerated lung. In a hemothorax, the pleural space becomes filled with blood. Normal lung expansion does not occur, and the lung itself is compressed, thus less air is inhaled. In addition, significantly less blood may be available to carry the reduced level of oxygen to the patient's vital organs.
To treat a hemothorax, the blood must be removed from the pleural space to allow the lung to expand to its normal capacity. Current day treatment of a hemothorax by a first responder includes application of an occlusive dressing over the wound, positioning the patient onto the injured side, thus limiting the pooled blood to the wounded side of the chest cavity, immediate ventilatory support, administration of oxygen, and immediate transportation to the hospital. Treatment by first responders does not currently include removal of the accumulated blood from the pleural space. Some type of valved dressing may also be used for hemothorax treatment in this situation, such as the flexible valve dressing described in U.S. Pat. No. 5,478,333.
Finally, first response on the battlefield is complicated by the hostile environment in which it normally occurs. Any treatment must be easy to use and adapted to the rigors of the battlefield environment. For example, medics on the battlefield providing first response often, after placing dressings on a wounded soldier, replace the soldier's chest protecting body armor in order to protect the soldier until such time as the soldier can be removed from the hostile environment. In addition, battlefield transport and conditions often require that the patient be placed on the wounded side. If the patient is suffering from a tension pneumothorax or a hemothorax, these situations have the effect of subjecting the dressing used to external compression and pressure, potentially crushing any delicate portion of the dressing and/or interfering with the dressing's ability to allow trapped fluids to escape, such as in the case of the three-sided dressing and the flexible valve dressing designs discussed above.